Vehicle seat assembly having a hardness gradient via &#34;a&#34; surface intrusions and/or protrusions

ABSTRACT

In at least one embodiment, the present invention provides a vehicle seat assembly comprising a cushion having an “A” surface and a “B” surface, a central portion, and two bolster areas, with each bolster area being adjacent the central portion, with the cushion having a plurality of intrusions extending from the “A” surface towards the “B” surface to form a hardness gradient between at least one of the bolster areas and the central portion of between 8% to 25%.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vehicle seat assembly having ahardness gradient and method of making the same. More specifically, thepresent invention relates to a vehicle seat assembly having areas thatare configured to be less hard than other areas of the seat assembly andmethods of making the same.

2. Background Art

Generally speaking, a vehicle seat assembly includes three fundamentalcomponents: (a) a frame to support the seat assembly and to mount it toa vehicle; (b) a foam cushion to cover the frame; and (c) trim materialto cover the foam cushion and provide a durable surface for contact witha vehicle occupant. Typically, the foam cushion is made from anexpandable foam material, such as polyurethane, and is molded to apredetermined shape during a molded process. For example, thepredetermined shape of a typical bucket-style seat includes raisedfront, side, and rear bolster areas and recessed central seating andback sections. The trim material may include any number of materials,such as cloth, polymers, or leather. Often, the selection of trimmaterial is governed by the sale price of the vehicle. For example,leather trim material may be used for luxury vehicles while cloth andpolymeric materials may be used for less expensive vehicles.

An important consideration in the manufacture of seat cushions is toprovide inboard and outboard portions of the seat cushion which arerelatively resistant to premature wear while providing an insert orcenter portion which is soft and comfortable. Inboard and outboard sidesof the vehicle seat assembly typically bear most of the load when theoccupant gets in and out of the vehicle and therefore require additionalrigidity relative to the center insert portion of the vehicle seatassembly. Presently, there is no relatively inexpensive and simple wayof providing a vehicle seat assembly having more rigid inboard and/oroutboard bolster areas relative to the center insert area.

Accordingly, there is a need to provide a vehicle seat assembly whichhas a seat cushion that has a relatively rigid outboard and inboardbolster area and a relatively less rigid center portion area which canbe manufactured easily and relatively economically.

SUMMARY OF THE INVENTION

According to at least one aspect of the present invention, a vehicleseat assembly is provided. In at least one embodiment, the vehicle seatassembly comprises a cushion having an “A” surface and a “B” surface, acentral portion, and two bolster areas, with each bolster area beingadjacent the central portion. In at least this embodiment, the cushionhas a plurality of intrusions extending from the “A” surface towards the“B” surface to form a hardness gradient between at least one of thebolster areas and the central portion of between 8% to 25%. Cushionshaving a hardness gradient of 8% to 25% between the central portion andat least one bolster area will have a desirable comfort, durability,vibration resistance, and safety performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cut-away environmental view of a vehicle seat assembly inaccordance with an environment of the present invention;

FIG. 2 is a top perspective view of a bottom seat cushion useable withthe vehicle seat assembly illustrated in FIG. 1;

FIG. 3 is a cross-sectional view of the seat cushion illustrated in FIG.2;

FIG. 4 is a view similar to FIG. 2 showing another embodiment of thepresent invention;

FIG. 5 is a cross sectional view illustrating another embodiment of abottom seat cushion useable with the seat assembly of the presentinvention;

FIG. 6 is a view similar to FIG. 5 showing another embodiment of thepresent invention;

FIG. 7 is a view similar to FIG. 5 showing yet another embodiment of thepresent invention;

FIG. 8 illustrates an example of occupant pressure modeling for a seatbottom cushion; and

FIG. 9 illustrates an example of occupant pressure modeling for a seatback cushion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As required, detailed embodiments of the present invention are disclosedherein. However, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to scale, somefeatures may be exaggerated or minimized to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for the claims and/or as a representative basis forteaching one skilled in the art to variously employ the presentinvention.

Moreover, except where otherwise expressly indicated, all numericalquantities in this description and in the claims are to be understood asmodified by the word “about” in describing the broader scope of thisinvention. Practice within the numerical limits stated is generallypreferred. Also, unless expressly stated to the contrary, thedescription of a group or class of materials by suitable or preferredfor a given purpose in connection with the invention implies thatmixtures of any two or more members of the group or class may be equallysuitable or preferred.

Referring now to the figures, where like numerals are used to designatelike structure throughout to the drawings, a schematic vehicle seatassembly in accordance with at least one embodiment of the presentinvention is generally shown at 10 in FIG. 1. While the vehicle seatassembly 10 is illustrated in FIG. 1 to be a bucket seat assembly, itshould be understood that the principles of the present invention areapplicable to other types of seat assemblies, such as bench, captain,and other types of seat assemblies. It should also be understood thatthe principles of the present invention are applicable to otherapplications where foam is a component such as back rests, back supportpads, arm rests, and head restraints.

As shown in FIG. 1, the vehicle seat assembly 10 includes a seat frame,generally indicated at 14 having a plurality of mounting brackets (notshown) adapted to operatively secure the seat frame within a vehicle.The seat frame 14 may be constructed from any material suitable forapplication within a vehicle seat assembly 10, such as aluminum, steelor other metal alloy or a suitable polymer. Further, the seat frame 14may be manufactured using a technique commonly known in the art,relative to the type of material employed. By way of example,manufacturing techniques may include stamping, welding, fastening ormolding a suitable material to form a seat frame 14.

The vehicle seat assembly 10 comprises a seat back, generally indicatedat 16, and a lower seat assembly, generally indicated at 18. In at leastthe illustrated embodiment, the seat back 16 includes a central backsupport pad 20, side bolsters 22, and trenches 24 between the bolsters22 and the pad 20. In at least the illustrated embodiment, the lowerseat assembly 18 includes a central seating pad 26, a plurality ofbolsters 30 and 31 substantially surrounding at least two opposingsides, and as shown here, three sides, of the central seating pad 26,and trenches 32 between the bolsters 30 and 31 and the pad 26. Bolsters30 are located at opposite sides (i.e., inboard and outboard) of thelower seat assembly 12 and the bolster 31 is located at the front of thelower seat assembly 18 and extends between and connects the frontportions of the bolsters 30.

The vehicle seat assembly 12 further includes a back foam cushion (notshown) and a seat foam cushion generally indicated at 34. The seat foamcushion 34 is conventionally secured to the seat frame 14 and/or a seatassembly infrastructure (not shown). The foam cushion 34 may be securedto the seat frame 14 and/or infrastructure by any method generally knownin the art, such as by an adhesive. It should be understood while thefoam cushion 34 is illustrated to be a bucket-seat bottom cushion, thepresent invention can be applicable to any type of seat cushion such asa seat back cushion for a bucket-seat and seat back and bottom cushionfor bench seats, as well as other types of seats.

The vehicle seat assembly 12 also includes a trim material 36 adapted toengage the foam cushion 34 (or cushions) in a covering relationship. Thetrim material 36 may include any material commonly known in the art. Byway of example, some of the known materials include cloth, leather, orpolymers of sufficient quality and thickness for use in seat trimapplications. Polymer trim materials may include a flexible closed cellpolymer skin material such as polyvinyl, polyvinyl chloride (PVC),thermoplastic olefin (TPO), or thermoplastic urethane (TPU).Additionally, materials for use as trim material 36 may include a foambacking (not shown, but generally known in the art) which may bemanufactured from a variety of polymer foam materials. By way ofexample, the foam backing may be polyethylene, polypropylene,polyurethane, or a polystyrene foam. Optionally, a mesh or reinforcingmaterial (not shown, but generally known in the art) such as fiberglassor nylon may be applied to the foam backing or back of the trim material36 for increasing strength without increasing rigidity.

The seat cushion 34 has an upper surface 38 and a lower surface 40 thatis spaced from the upper surface 38. The upper surface 38 of the seatcushion 34 may be referred to as the “A” surface, and the lower surface40 may be referred to as the “B” surface. The seat cushion 34 alsodefines an inboard side 42 and an outboard side 44. When an occupant(not shown) is supported on the lower seat assembly 18, the weight ofthe occupant will generally apply an axial load directed generallythrough the upper surface 38 of the seat cushion 34 towards the lowersurface 40. Although the weight of the occupant will generally induce anaxial as well as sheer force in the seat cushion 34, those havingordinary skill in the art will recognize that the primary load path ofthe occupant's weight will be substantially vertical from the uppersurface 38 towards the lower surface 40 through the seat cushion.However, when the occupant is getting in and out of the vehicle, anincreased and substantially sizeable load will typically be placed onthe inboard and outboard bolster portions 30 of the seat cushion 34.

In accordance with the present invention, a seat cushion 34 is providedthat has bolster portions 30 having a greater hardness relative to thecentral seating pad 26. In at least one embodiment, the bolster 31 alsohas a greater hardness relative to the central seating pad 26. Toprovide the desired hardness gradient, seat cushion 34 can be providedwith intrusions extending from the “A” surface 38 towards the “B”surface 40 in one or more of the bolster areas 30 and/or 31 and/or thecenter area 26 to provide a seat cushion 34 having varying hardnessareas. In at least another embodiment, the seat cushion 34 can furtherbe provided with protrusions extending from the “A” and/or the “B”surfaces 38 and 40 away from the other surface in the bolster areas 30and/or 31 and/or the center area 26 to provide a seat cushion 34 havingvarying hardness areas. For instance, the seat cushion 34 is configuredso that one or more (or all) of the bolsters 30 is harder than thecentral seating pad 26.

In at least one embodiment, the present invention enables themodification of the hardness of the foam primarily in the centralseating pad 26, i.e., areas of typical consumer contact while driving,while keeping the other areas of the seat cushion 34, i.e., the bolsters30 and 31, firmer to enable improved craftsmanship and durabilityperformance and provide lateral support to occupants while traveling oncurved roadways and during turning. Such a configuration enables thecentral seating pad 26 to be softer for improved occupant comfort whileallowing the bolster(s) 30 and/or 31 to be harder to account for thetypically higher loads placed upon the bolster(s) 30 and/or 31 uponoccupant ingress and egress. Such a configuration cal also assist theseat assembly 10 in achieving H-point specification withoutsignificantly modifying seat assembly packaging. In other words, theimplementation of intrusions and/or protrusions in accordance with thepresent invention can modify the seat cushion 34 in such a way thatallows the seat assembly 10 to achieve a desired H-point without havingto change the overall shape or size of the cushion 34. Additionally, theimplementation of intrusions (and in some instances the protrusions) canalso assist the seat assembly 10 in achieving a weight reduction and/orcost reduction.

While the harness gradient can generally be achieved by providingintrusions such as holes and/or other geometric openings that extendfrom the “A” surface 38 towards the “B” surface 40, and/or protrusionson the surfaces 38 and/or 40 of the seat cushion 34, it is contemplatedthat the location, size, and/or shape of the intrusions and/orprotrusions can vary as desired. However, in at least one embodiment,the seat cushion 34 of the present invention has a hardness gradientbetween at least one of the bolsters 30 and 31 and the central seatingpad 26 area of the seat cushion 34 of between 8% to 25%. In other words,at least one of the bolster areas 30 and 31 has a hardness that is atleast 8% to 25% greater than the hardness of the central seating pad 26.In at least certain embodiments, the seat cushion 34 has a hardnessgradient between the bolsters 30 and the central seating pad 26 ofbetween 8% to 25%. The hardness can be measured by indentation forcedeflection (IFD) as measured by ASTM test method No. D3574. In anotherembodiment, the seat cushion 34 of the present invention has a hardnessgradient between at least one of the bolsters 30 and 31 and the centralseating pad 26 of the seat cushion 34 of between 10% and 20%, and inother embodiments of between 12% and 18%.

In at least one embodiment, the hardness of the central seating pad 26of the seat cushion 34, as measured by ASTM test method No. D3574, isbetween 100 and 300 newtons, and in other embodiments between 150 and250 newtons. In at least another embodiment, the hardness of at leastone of the bolsters 30 and 31, as measured by ASTM test method D3574, isbetween 230 and 350 newtons, and in other embodiments between 250 to 300newtons. In at least certain embodiments, the hardness of each of thebolsters 30 and 31, as measured by ASTM test method D3574, is between230 and 350 newtons and in other embodiments between 250 and 300newtons.

Furthermore, in at least one embodiment, the seat cushion 34 of thepresent invention has a hysterisis loss gradient between at least one ofthe bolsters 30 and 31 and the central seating pad 26 area of the seatcushion 34 are between 8% to 25%. In other words, at least one bolsterarea has a hysterisis loss that is at least 8% to 25% less than thehysterisis loss of the central seating pad 26. The hysterisis loss canbe measured by indentation force deflection (IFD) as measured by ASTMtest method No. D3574. In another embodiment, the seat cushion 34 of thepresent invention has a hysterisis loss gradient between at least one ofthe bolsters 30 and the central seating pad 26 of the seat cushion 34 ofbetween 10% and 20%, and in other embodiments of between 12% and 18%.

In at least one embodiment, the front bolster 31 has a lower hardnessgradient relative to the central seating pad 26 than one or both of theside bolsters 30 to provide a front bolster 31 that is softer (primarilyfor comfort) than at least one of the side bolsters 30. In thisembodiment, the front bolster has a hardness of 150 to 300 newtons, andin other embodiments of 200 to 250 newtons. In this embodiment, thehardness gradient between the front bolster 31 and at least one of thecentral seating pad 26 is 5% to 20%, and the hardness gradient betweenthe front bolster 31 and the side bolsters 30 is 8% to 25%. In at leastone other embodiment, the hardness gradient between the front bolster 31and the central seating pad 26 is 8% to 18%, and the hardness gradientbetween at least one of the front bolster 31 and the side bolsters 30 is10% to 22%.

Referring to FIGS. 2 and 3, schematic perspective and cross-sectionalviews of an embodiment of a seat cushion 34 is shown. In thisembodiment, the central seating pad 26 has a number of openings or holes50 that extend from the “A” surface 38 towards the “B” surface 40. In atleast one embodiment, the holes 50 include a generally axial, generallycylindrical wall 46 that extends between and connects the “A” surface 38with a generally transverse hole bottom surface 48. In at least oneembodiment, hole bottom surface 48 is spaced 0.1 to 5 cm from the “A”surface 38, in at least another embodiment 0.5 to 3.25 cm, and in yetanother embodiment 1 to 2.5 cm.

While the openings 50 are shown to be circular, it should be understoodthat the openings 50 can vary in size and shape as desired. Forinstance, while the openings 50 are shown to be cylindrical holes, itshould be understood that they could be channels and/or slots, and/orfrustoconical, conical, polygonyl or other geometric cutouts, such asrectangles, squares, triangles, honeycombs (as will be disclosed below),etc.

While the location, size and/or shape of the openings 50 and projections52 can vary as desired, in at least one embodiment, the location, sizeand/or shape of the openings and/or projections can be selected basedupon a counter response to pressure input of an average measurement ofdemographic matching consumers in static and dynamic measured clinics inthe vehicle. FIGS. 8 and 9 illustrate examples of average pressuremodeling of demographic matching consumers for a seat cushion and a seatback, respectively. In FIG. 8, area a displays a pressure range of 1 to20.9 mm Hg of pressure, area b displays a pressure range of 30 to 40.88mm Hg of pressure, area c displays a pressure range of 40.9 to 60.8 mmHg of pressure, area d displays a pressure range of 60.9 to 80.6 mm Hgof pressure, and area e displays a pressure range of 80.7 to 101 mm Hgof pressure. In FIG. 9, area f displays a pressure range of 1 to 10.9 mmHg of pressure, area g displays a pressure range of 11 to 20.8 mm Hg ofpressure, and area h displays a pressure range of 20.9 to 30.7 mm Hg ofpressure.

In at least one embodiment, the cushion 34 can be tuned with openings 50and/or projections 52 to provide areas of lower hardness in areas ofexpected higher occupant pressure. Thus, in at least one embodiment, theareas of expected higher occupant pressure will have less openings 50and/or projections 52 and/or smaller openings than areas of expectedlower occupant pressure.

FIGS. 2, 4 and 7 illustrate a few examples of different openings 50and/or projections 52 configurations. In at least the embodimentillustrated in FIG. 2, there are 16 openings 50 in the “A” surface 38 ofthe cushion 34. However, it should be understood the number, size,shape, and/or location of openings 50 can vary as desired. In at leastthe embodiment illustrated in FIG. 2, the front bolster 31 has twoopenings 50 whereas the side bolsters 30 have none. This enables thefront bolster 31 to have a lower hardness gradient relative to thecentral seating pad 26 than the side bolsters 30. While the frontbolster 31 is illustrated in FIG. 2 as having two openings 50, it shouldbe understood that the front bolsters could have less or more openingsas desired.

In at least the embodiment illustrated in FIG. 2, the central seatingpad 26 is divided into two halves, a front half 26 a and a rear half 26b, as schematically shown by imaginary dashed line 27. In at least thisembodiment, the rear half 26 b has a lower hardness gradient relative tothe side bolsters 30 than the front half 26 a to provide a front half 26a that is softer (primarily for comfort) than the rear half 26 b. In atleast this embodiment, the front half 26 a of the central seating pad 26could have a hardness of 150 to 250 newtons and the rear half 26 b couldhave a hardness of 200 to 350 newtons. In at least this embodiment, thefront half 26 a of the central seating pad 26 could have a hardnessgradient relative to the side bolster 30 of 8 to 15% and the rear half26 b could have a hardness gradient relative to the side bolster 30 of12 to 25%.

While the front half 26 a and the rear half 26 b are illustrated in FIG.2 as having eight and six openings 50, respectively, it should beunderstood that the number of openings 50 in each half 26 a and 26 bcould vary as desired. While it should be understood that the size andshape of the openings 50 can vary as desired, in at least oneembodiment, the openings 50 have a diameter of 0.2 to 5 cm., in otherembodiments of 0.5 to 3.25 cm., and in yet other embodiments of 1 to 2.5cm. Furthermore, in at least one embodiment, the openings 50 have and adepth or length of 0.1 to 5 cm., in other embodiments of 0.25 to 2.5cm., and in yet other embodiments of 0.5 to 2 cm. Moreover, in at leastone embodiment, it has been found useful to provide the openings 50 witha radius of 4 to 15 mm, and in other embodiments of 6 to 12 mm, toassist in the molding of the seat cushion.

FIG. 4 illustrates another embodiment of the seat cushion 34. In thisembodiment, protrusions 52 can be provided on the “A” surface 38 and/or“B” surface 40 of the seat pad 26. The protrusions 52 extend away fromthe “A” surface and/or the “B” surface 40. Like the openings 50, theprotrusions 52 can vary in size, shape, location, and/or number asdesired. The protrusions 52 help to provide desirable force resistanceproperties for the pad 26 in response to comfort, vibration and/or shockinputs. For instance, the protrusions 52 can provide reinforcement atlocalized points of contact and/or provide lower or higher hardnessareas relative to their surrounding regions.

In at least one embodiment, the protrusions 52 have a length of 0.2 to 5cm., in other embodiments of 0.5 to 3.25 cm., and in yet anotherembodiment of 1 to 2.5 cm. In at least one embodiment, the protrusions52 have a width of 0.5 to 5 cm., in other embodiments of 0.5 to 3.25cm., and in yet another embodiment of 1 to 2.5 cm. In at least oneembodiment, the protrusions 52 have a height of 0.1 to 5 cm, in otherembodiments of 0.25 to 2.5 cm., and in yet other embodiments of 0.5 to 2cm. Moreover, in at least another embodiment, each of the protrusions 52have a depth or length that is 5% to 50% of the total depth or thicknessof the cushion 34 in the area of the respective protrusion, in otherembodiments of 10% to 40% of the total depth or thickness of the cushionin the area of the respective protrusion, and in yet other embodimentsof 15% to 35% of the total depth or thickness of the cushion in the areaof the respective protrusion. It should be understood that the size,shape, and/or geometry of the openings 50 and/or protrusions 52 can varyfrom each other. For instance, one opening can be different in size,shape, and/or geometry from another opening 50 and/or protrusion 52.

Moreover, while the openings 50 can be provided to provide a densityand/or hardness gradient to tailor the specific comfort requirements ofthe seat assembly, the openings 50 could also be used to reduce weightof the overall seat assembly, and in particular the foam cushion 34. Forinstance, the foam could be cored to have intrusions such as holesand/or channels in areas of large seating surfaces such as armrestsand/or center portions between seat occupants. Furthermore, as discussedabove, the openings 50 can be provided to assist the seat assembly 10 inachieving a desired H-point and/or cost reduction. Moreover, while theseat assembly 10 has been described as having bolster portion(s) thatare harder than the remainder of the seat assembly, it should beunderstood that the principles of the present invention can be used tomanufacture seat assemblies having areas of the seat assemblies that areharder, or at least as hard, as one or more of the bolsters.

The seat cushion 34 of the present invention can be made by a variety ofmethods. In at least one embodiment, the seat cushion 34 is made bymolding wherein the intrusions and/or protrusions are molded into theseat cushion 34 during the molding operation. In this embodiment, thefoam molding tool can be provided with protrusions and/or cavitiesaround and/or within which the foam can be molded. In at least oneembodiment, it has been found useful to provide molding tools havingmolding surfaces that result in openings 50 and/or protrusions 52 havinga radius of 4 to 15 mm, and in other embodiments of 6 to 12 mm, toassist in the molding of the seat cushion.

Referring to FIG. 5, in at least another embodiment, intrusions(openings) 50 and/or protrusions 52 are molded into a foam sub-assembly60 which is then secured to a seat bottom 62 not having protrusionsand/or opening (at least a substantial amount which would cause thenecessary density gradient). It should be understood that othermanufacturing means could be used, such as die-cutting the openings 50.In at least one embodiment, the seat bottom 62 has the “B” surface 40and the subassembly 60 has the “A” surface 38, however, it should beunderstood that this configuration could be reversed. Referring to FIG.6, the seat bottom 62 has a cavity 66 within which sub-assembly 60 isreceived. In these embodiments, the subassembly 60 can be secured to theseat bottom 62 by any suitable method such as adhesion and/or fasteners.

FIG. 7 illustrates an embodiment where the openings 50 and protrusions52 are honey-combed in shape. The honeycomb shape can provide anincreased structural integrity relative to other shapes. For instance,the hexahedral wall structure can provide a relatively high forceresistance efficiency. While the openings 50 and the protrusions 52 areshown to be the same shape in FIG. 7, it should be understood that theopenings 50 could be shaped differently than the protrusions 52.

While embodiments of the invention have been illustrated and described,it is not intended that these embodiments illustrate and describe allpossible forms of the invention. Moreover, the words used in thespecification are words of description rather than limitation, and it isunderstood that various changes may be made without departing fromspirit and scope of the invention.

1. A vehicle seat assembly comprising: a cushion having an “A” surfaceand a “B” surface, a central portion, and two bolster areas, with eachbolster area being adjacent the central portion, the cushion having aplurality of intrusions extending from the “A” surface towards the “B”surface to form a hardness gradient between at least one of the bolsterareas and the central portion of between 8% to 25%.
 2. The vehicle seatassembly of claim 1 wherein the at least one bolster areas has ahardness that is at least 8% to 25% greater than the hardness of thecentral portion.
 3. The vehicle seat assembly of claim 1 wherein thecentral portion has holes formed in the “A” surface of the centralportion to provide a reduced hardness relative to the at least one ofthe bolster areas.
 4. The vehicle seat assembly of claim 3 wherein theholes have a diameter of 0.2 to 5.0 cm. and a length of 0.1 to 5 cm. 5.The vehicle seat assembly of claim 4 wherein the cushion comprises amolded foam cushion and the holes are formed during the molding of thecushion.
 6. The vehicle seat assembly of claim 4 wherein the holes areformed on a sub cushion assembly that is attached to a main cushionassembly.
 7. The vehicle seat assembly of claim 3 wherein the “A”surface has protrusions formed therein.
 8. The vehicle seat assembly ofclaim 7 wherein the protrusions extend from the “A” surface, away fromthe “B” surface, a distance of 0.1 to 5.0 cm.
 9. The vehicle seatassembly of claim 1 wherein the cushion comprises a seat bottom cushion,with the central portion having a front half having a lower hardnessthan the rear half.
 10. A vehicle seat assembly comprising: a cushionhaving an “A” surface and a “B” surface, a central portion, two sidebolster area adjacent the central portion, and a front bolster areaextending between and connecting the side bolster areas, wherein thecentral portion of the cushion has a first plurality of intrusionsextending from the “A” surface towards the “B” surface to form ahardness gradient between at least one of the side bolster area and thecentral portion of between 8% to 25%, and the front bolster area has asecond plurality of intrusions, less than the first plurality ofintrusions, extending from the “A” surface towards the “B” surface toform a hardness gradient between the front bolster area and the centralportion of 5% to 20%.
 11. The vehicle seat assembly of claim 10 whereinthe central portion comprises a front half adjacent the front bolsterarea and a rear half spaced from the front bolster area and adjacent thefront half, the front half having a hardness gradient relative to atleast one of the side bolster areas of between 8% to 15% and the rearhalf having a hardness gradient relative to at least one of the sidebolster areas of between 12% to 25%.
 12. A method of making a vehicleseat assembly, the method comprising: providing a cushion having an “A”surface and a “B” surface, a central portion, and two bolster areas,with each bolster area being adjacent the central portion, the cushionhaving a plurality of intrusions extending from the “A” surface towardsthe “B” surface to form a hardness gradient between at least one of thebolster areas and the central portion of between 8% to 25%; securing thecushion to a frame; and covering the cushion with a trim member.
 13. Themethod of claim 12 wherein the at least one bolster areas has a hardnessthat is at least 8% to 25% greater than the hardness of the centralportion.
 14. The method of claim 12 wherein the providing step comprisesmolding a polymeric material to form a foam cushion.
 15. The method ofclaim 14 wherein the central portion has holes formed in the “A” surfaceof the center area to provide a reduced hardness relative to the atleast one bolster area.
 16. The method of claim 15 wherein the holeshave a diameter of 0.2 to 5.0 cm. and a length of 0.1 to 5 cm.
 17. Themethod of claim 15 wherein the holes are formed during the molding ofthe cushion.
 18. The method of claim 15 wherein the location, shapeand/or size of the holes are based upon occupant pressure modeling. 19.The method of claim 18 wherein an area of the central portion determinedto be subjected to a relatively high occupant pressure has less and/orsmaller holes than an area of the central portion determined to besubjected to a relatively low occupant pressure.
 20. The method of claim16 wherein the holes are formed on a sub cushion assembly that isattached to a main cushion assembly.